Boron citrate esters as boron daily food supplementing agents. Synthesis and structural characterizations

Boric acid, H3BO3, is a weak acid and is in the form of an uncharged small molecule at physiological pH. Acting as a Lewis acid, it forms complexes (esters) with amino and hydroxy acids, carbohydrates, nucleotides and vitamins through electron donor-acceptor interactions. These interactions are believed to be beneficial for human health. Therefore, synthetic bichelate complexes of boric acid with organic biomolecules are considered for nutritional and/or pharmaceutical applications. Research is needed to better elucidate the mechanisms of action of boron and to identify requirements in different areas. In this study, the complexation of citric acid, which is widely used in the food industry, with boric acid was investigated considering that it would be more beneficial in bio applications. Mono-chelate (1:1) and bichelate (1:2) anionic complexes of citric acid and boric acid, which are thought to be used as food supplements, were isolated from aqueous solutions in salt form with K+, Mg+2, Na+ and Ca+2 ions. The complexes were characterized by elemental analysis, FT-IR, X-ray crystallography and thermal methods.